package hot;


class ListNode {
      int val;
      ListNode next;
      ListNode() {}
      ListNode(int val) { this.val = val; }
      ListNode(int val, ListNode next) { this.val = val; this.next = next; }
  }
public class num2 {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = null,tail = null;
        int carry = 0;
        while(l1 != null || l2 != null) {
            int t1 = l1 == null ? 0 : l1.val;
            int t2 = l2 == null ? 0 : l2.val;
            int sum = t1 + t2 + carry;
            if(head == null) {
                head = tail = new ListNode(sum % 10);
            }else {
                tail.next = new ListNode(sum % 10);
                tail = tail.next;
            }
            carry = sum / 10;
            if(l1 != null) {
                l1 = l1.next;
            }
            if(l2 != null) {
                l2 = l2.next;
            }
        }
        if(carry != 0) {
            tail.next = new ListNode(carry);
            tail = tail.next;
        }
        return head;
    }
}
